The invention relates to systems and methods for preparing a sample for analysis, and more specifically to systems and methods for dispensing low volumes of fluid material onto a substrate surface for generating an array of samples for diagnostic analysis.
In recent years, developments in the field of life sciences have proceeded at a breathtaking rate. Universities, hospitals and newly formed companies have made groundbreaking scientific discoveries and advances that promise to reshape the fields of medicine, agriculture, and environmental science. However, the success of these efforts depends, in part, on the development of sophisticated laboratory tools that will automate and expedite the testing and analysis of biological samples. Only upon the development of such tools can the benefits of these recent scientific discoveries be achieved fully.
At the forefront of these efforts to develop better analytical tools is a push to expedite the analysis of complex biochemical structures. This is particularly true for human genomic DNA, which is comprised of at least about one hundred thousand genes located on twenty four chromosomes. Each gene codes for a specific protein, which fulfills a specific biochemical function within a living cell. Changes in a DNA sequence are known as mutations and can result in proteins with altered or in some cases even lost biochemical activities; this in turn can cause a genetic disease. More than 3,000 genetic diseases are currently known. In addition, growing evidence indicates that certain DNA sequences may predispose an individual to any of a number of genetic diseases, such as diabetes, arteriosclerosis, obesity, certain autoimmune diseases and cancer. Accordingly, the analysis of DNA is a difficult but worthy pursuit that promises to yield information fundamental to the treatment of many life threatening diseases.
Unfortunately, the analysis of DNA is made particularly cumbersome due to size and the fact that genomic DNA includes both coding and non-coding sequences (e.g., exons and introns). As such, traditional techniques for analyzing chemical structures, such as the manual pipeting of source material to create samples for analysis, are of little value. To address the scale of the necessary analysis, scientist have developed parallel processing protocols for DNA diagnostics.
For example, scientists have developed robotic devices that eliminate the need for manual pipeting and spotting by providing a robotic arm that carries at its proximal end a pin tool device that includes a matrix of pin elements. The individual pins of the matrix are spaced apart from each other to allow each pin to be dipped within a well of a microtiter plate. The robotic arm dips the pins into the wells of the microtiter plate thereby wetting each of the pin elements with sample material. The robotic arm then moves the pin tool device to a position above a target surface and lowers the pin tool to the surface contacting the pins against the target to form a matrix of spots thereon. Accordingly, the pin tool expedites the production of samples by dispensing sample material in parallel.
Although this pin tool technique works well to expedite the production of sample arrays, it suffers from several drawbacks. First during the spotting operation, the pin tool actually contacts the surface of the substrate. Given that each pin tool requires a fine point in order that a small spot size is printed onto the target, the continuous contact of the pin tool against the target surface will wear and deform the fine and delicate points of the pin tool. This leads to errors which reduce accuracy and productivity.
An alternative technique developed by scientists employs chemical attachment of sample material to the substrate surface. In one particular process, DNA is synthesized in situ on a substrate surface to produce a set of spatially distinct and diverse chemical products. Such techniques are essentially photolithographic in that they combine solid phase a chemistry, photolabile protecting groups and photo activated lithography. Although these systems work well to generate arrays of sample material, they are chemically intensive, time consuming, and expensive.
It is further troubling that neither of the above techniques provide sufficient control over the volume of sample material that is dispensed onto the surface of the substrate. Consequently, error can arise from the failure of these techniques to provide sample arrays with well controlled and accurately reproduced sample volumes. In an attempt to circumvent this problem, the preparation process will often dispense generous amounts of reagent materials. Although this can ensure sufficient sample volumes, it is wasteful of sample materials, which are often expensive and of limited availability.
Even after the samples are prepared, scientists still must confront the need for sophisticated diagnostic methods to analyze the prepared samples. To this end, scientists employ several techniques for identifying materials such as DNA. For example, nucleic acid sequences can be identified by hybridization with a probe which is complementary to the sequence to be identified. Typically, the nucleic acid fragment is labeled with a sensitive reporter function that can be radioactive, fluorescent, or chemiluminescent. Although these techniques can work well, they do suffer from certain drawbacks. Radioactive labels can be hazardous and the signals they produce decay over time. Nonisotopic (e.g. fluorescent) labels suffer from a lack of sensitivity and fading of the signal when high intensity lasers are employed during the identification process. In addition, labeling is a laborious and time consuming error prone procedure.
Consequently, the process of preparing and analyzing arrays of a biochemical sample material is complex and error prone.
Accordingly, it is an object herein to provide improved systems and methods for preparing arrays of sample material.
It is a further object to provide systems that allow for the rapid production of sample arrays.
It is yet another object to provide systems and methods for preparing arrays of sample material that are less expensive to employ and that conserve reagent materials.
It is a further object to provide systems and methods for preparing arrays of sample material that provide high reproducibility of the arrays generated.
Other objects of the apparatus and methods provided herein will be apparent from the description also disclosed in the following.
Serial and parallel dispensing tools that can be employed to generate multi-element arrays of sample material on a substrate surface are provided. The substrates surfaces can be flat or geometrically altered to include wells of receiving material. In one embodiment, a tool that allows the parallel development of a sample array is provided. To this end, the tool can be understood as an assembly of vesicle elements, or pins, wherein each of the pins can include a narrow interior chamber suitable for holding nano liter volumes of fluid. Each of the pins can fit inside a housing that itself has in interior chamber. The interior housing can be connected to a pressure source that will control the pressure within the interior housing chamber to regulate the flow of fluid through the interior chamber of the pins. This allows for the controlled dispensing of defined volumes of fluid from the vesicles. In an alternative embodiment, the invention provides a tool that includes a jet assembly that can include a capillary pin having an interior chamber, and a transducer element mounted to the pin and capable of driving fluid through the interior chamber of the pin to eject fluid from the pin. In this way, the tool can dispense a spot of fluid to a substrate surface by spraying the fluid from the pin. Alternatively, the transducer can cause a drop of fluid to extend from the capillary so that fluid can be passed to the substrate by contacting the drop to the surface of the substrate. Further, the tool can form an array of sample material by dispensing sample material in a series of steps, while moving the pin to different locations above the substrate surface to form the sample array. In a further embodiment, the invention then passes the prepared sample arrays to a plate assembly that disposes the sample arrays for analysis by mass spectrometry. To this end, a mass spectrometer is provided that generates a set of spectra signal which can be understood as indicative of the composition of the sample material under analysis.
To this end a dispensing apparatus for dispensing defined volumes of fluid, including nano and sub-nano volumes of fluid, in chemical or biological procedures onto the surface of a substrate is provided. The apparatus provided herein can include a housing having a plurality of sides and a bottom portion having formed therein a plurality of apertures, the walls and bottom portion of the housing defining an interior volume; one or more fluid transmitting vesicles, or pins, mounted within the apertures, having a nanovolume sized fluid holding chamber for holding nanovolumes of fluid, the fluid holding chamber being disposed in fluid communication with the interior volume of the housing, and a dispensing element that is in communication with the interior volume of the housing for selectively dispensing nanovolumes of fluid form the nanovolume sized fluid transmitting vesicles when the fluid is loaded with the fluid holding chambers of the vesicles. As described herein, this allows the dispensing element to dispense nanovolumes of the fluid onto the surface of the substrate when the apparatus is disposed over and in registration with the substrate.
In one embodiment the fluid transmitting vesicle has an open proximal end and a distal tip portion that extends beyond the housing bottom portion when mounted within the apertures. In this way the open proximal end can dispose the fluid holding chamber in fluid communication with the interior volume when mounted with the apertures. Optionally, the plurality of fluid transmitting vesicles are removably and replaceably mounted within the apertures of the housing, or alternatively can include a glue seal for fixedly mounting the vesicles within the housing.
In one embodiment the fluid holding chamber includes a narrow bore dimensionally adapted for being filled with the fluid through capillary action, and can be sized to fill substantially completely with the fluid through capillary action.
In one embodiment, the plurality of fluid transmitting vesicles comprise an array of fluid delivering needles, which can be formed of metal, glass, silica, polymeric material, or any other suitable material.
In one embodiment the housing can include a top portion, and mechanical biasing elements for mechanically biasing the plurality of fluid transmitting vesicles into sealing contact with the housing bottom portion. In one particular embodiment, each fluid transmitting vesicle has a proximal end portion that includes a flange, and further includes a seal element disposed between the flange and an inner surface of the housing bottom portion for forming a seal between the interior volume and an external environment. The biasing elements can be mechanical and can include a plurality of spring elements each of which are coupled at one end to the proximal end of each of the plurality of fluid transmitting vesicles, and at another end to an inner surface of the housing top portion. The springs can apply a mechanical biasing force to the vesicle proximal end to form the seal.
In a further embodiment, the housing further includes a top portion, and securing element for securing the housing top portion to the housing bottom portion. The securing element can comprise a plurality of fastener-receiving apertures formed within one of the top and bottom portions of the housing, and a plurality of fasteners for mounting within the apertures for securing together the housing top and bottom portions.
In one embodiment the dispensing element can comprise a pressure source fluidly coupled to the interior volume of the housing for dispensing the interior volume at a selected pressure condition. Moreover, in an embodiment wherein the fluid transmitting vesicles are filled through capillary action, the dispensing element can include a pressure controller that can vary the pressure source to dispense the interior volume of the housing at varying pressure conditions. This allows the controller varying element to dispense the interior volume at a selected pressure condition sufficient to offset the capillary action to fill the fluid holding chamber of each vesicle to a predetermined height corresponding to a predetermined fluid amount. Additionally, the controller can further include a fluid selection element for selectively discharging a selected nanovolume fluid amount from the chamber of each vesicle. In one particular embodiment, the apparatus includes a pressure controller that operates under the controller of a computer program operating on a data processing system to provide variable control over the pressure applied to the interior chamber of the housing.
In one embodiment the fluid transmitting vesicle can have a proximal end that opens onto the interior volume of the housing, and the fluid holding chamber of the vesicles are sized to substantially completely fill with the fluid through capillary action without forming a meniscus at the proximal open end. Optionally, the apparatus can have plural vesicles, wherein a first portion of the plural vesicles include fluid holding chambers of a first size and a second portion including fluid holding chambers of a second size, whereby plural fluid volumes can be dispensed.
In another embodiment the apparatus can include, a fluid selection element that has a pressure source coupled to the housing and in communication with the interior volume for dispensing the interior volume at a selected pressure condition, and an adjustment element that couples to the pressure source for varying the pressure within the interior volume of the housing to apply a positive pressure in the fluid chamber of each fluid transmitting vesicle to vary the amount of fluid dispensed therefrom. The selection element and adjustment element can be computer programs operating on a data processing system that directs the operation of a pressure controller connected to the interior chamber.
In a further alternative embodiment, an apparatus for dispensing a fluid in chemical or biological procedures into one or more wells of a multi-well substrate is provided. The apparatus can include a housing having a plurality of sides and a bottom portion having formed therein a plurality of apertures, the walls and bottom portion defining an interior volume, a plurality of fluid transmitting vesicles, mounted within the apertures, having a fluid holding chamber disposed in communication with the interior volume of the housing, and a fluid selection and dispensing means in communication with the interior volume of the housing for variably selecting am amount of the fluid loaded within the fluid holding chambers of the vesicles to be dispensed from a single set of the plurality of fluid transmitting vesicles. Accordingly, the dispensing means dispenses a selected amount of the fluid into the wells of the multi-well substrate when the apparatus is disposed over and in registration with the substrate.
In yet another embodiment, a fluid dispensing apparatus for dispensing fluid in chemical or biological procedures into one or more wells of a multi-well substrate, that includes a housing having a plurality of sides and top and bottom portions, the bottom portion having formed therein a plurality of apertures, the walls and top and bottom portions of the housing defining an interior volume, a plurality of fluid transmitting vesicles, mounted within the apertures, having a fluid holding chamber sized to hold nanovolumes of the fluid, the fluid holding chamber being disposed in fluid communication with the volume of the housing, and mechanical biasing element for mechanically biasing the plurality of fluid transmitting vesicles into sealing contact with the housing bottom portion is provided.